Forming expanded mesh sheet from deformable strip

ABSTRACT

A method and an apparatus are disclosed for forming expanded mesh sheet from deformable strip by the steps of concurrently slitting and preforming the strip to provide transverse bands of slit and elongated wire segments projecting alternately from opposite sides of the plane of the strip separated by transverse bands of unslit strip, slitting the strip at alternate bands to extend slit segments in a staggered relation and laterally expanding the slit and preformed strip. Concurrent slitting and preforming and subsequent slitting can be effected by a cluster of three rolls or by a linear arrangement of pairs of opposed rolls. 
     The invention has particular utility in forming expanded mesh sheet of exact final dimensions for use as battery grids from lead or lead alloy strip.

This is a division of application Ser. No. 970,298 filed Dec. 18, 1978.

BACKGROUND OF THE INVENTION

The process and apparatus of the present invention relate to the rapidproduction of expanded mesh sheet, e.g., the expansion of a portion ofmetal strip contained within unexpanded imperforate border portions forthe manufacture of grids, particularly grids used in pasted batteryelectrodes.

In conventional preparation of strip by rotary slitting to permitlateral expansion which forms a network of meshes, e.g. the method shownin FIGS. 8 and 9 of U.S. Pat. No. 1,472,769, longitudinally alignedslits arranged in a staggered relation may be cut into a strip byengagement between a pair of opposed rolls, each roll comprising spaceddiscs having circular cutting edges interrupted by recesses which arespaced circumferentially. On rotation of the rolls, recesses in thediscs of one roll become aligned with like recesses in the discs of theother roll to leave spaced unslit portions of strip which become nodeshaving bonds that join adjacent strand-like components in the staggeredrelation. In this slitting operation, the discs of one roll pressalternate strand-like components out of the plane of the strip in onedirection while the discs of the other roll press interveningstrand-like components out of the plane of the strip in the oppositedirection. Some bending and stretching of bonds connecting adjacentstrand-like components occur in this operation, and during lateralexpansion to provide a network of meshes, to impose additional forces onthe bonds. If the network of meshes is to be contained within unexpandedimperforate border portions, preforming or elongation of the strand-likecomponents is required to compensate for shortening during expansion ofthe slit area relative to the border portions. Otherwise irregularripples will form in the imperforate borders or these borders willrequire corrugation to provide uniform shortening to the length of meshportion. In the slitting, preforming and lateral expansion in successivesteps of strip material, particularly strip material having low tensilestrength such as lead or lead alloys, bonds between strand-likecomponents may become points of weakness which can be prone to failureduring subsequent use.

The method of U.S. Pat. No. 1,472,769 provides zones of expanded metalbetween non-expanded longitudinal strips or ribs without shortening theslit portion of strip. Strip is slit as previously described, thenflattened into the original plane. Flattened strip moves betweencorrugating rolls which coact to press alternate series of bonds, i.e.rows of bonds connecting laterally adjacent components, out of the planeof the strip. This causes strands to be stretched and to be inclinedlaterally. Divergence of the side strips opens meshes which are thenflattened. It is considered undesirable to stretch the strands by asingle operation to a sufficient length to accommodate a full lateralexpansion of the meshes. Use of successive corrugating and expandingoperations overcomes resilience of the metal. Final flattening of theexpanded meshes sets the corrugated bonds and inclined strands in acommon plane.

In the method of U.S. Pat. No. 1,212,863, stretching of components in aslit portion of strip is effected by moving alternate nodes of eachcomponent out of the plane of the strip. Successively acting diesprovide both slitting and stretching as the strip advances. Since thedies act successively, the strip must be moved through the assemblyintermittently.

U.S. Pat. No. 1,205,299 illustrates, in FIG. 3, shaping rolls comprisingdiscs which taper into relatively thin peripheral edges made up ofuniform and regularly alternating notches and gripping projections.These rolls, although similar in longitudinal section to slitting andpreforming rolls of the present invention, are used to expand moreuniformly strip which has been slit and preformed intermittently in apreceding die press.

Elongation of strands preslit by rotary cutting and subsequent lateralexpansion often leads to breakage of the strands due to excessstretching or to failure of the strands at node bonds due toconcentration of stresses at the nodes.

In the forming of meshes from strip by reciprocal techniques, e.g. themethod of U.S. Pat. No. 1,482,600, stretching of bonds between adjacentstrand-like components occurs during progressive slitting and opening ofmeshes using reciprocating cutting tools wherein individual wiresegments are cut from strip and stretched out of the plane of the stripby the reciprocating cutters. Twisting of nodes during deformation bythe reciprocating cutting tools and subsequent bending as meshes arebrought into the plane of expanded sheet impose stresses on the nodalbonds joining the strand-like components. Product having imperforateborders may be obtained by the reciprocating technique but this methodis sensitive to changes in strip material dimensions which can adverselyaffect final dimensions and is limited in speed of production.

SUMMARY OF THE INVENTION

In the method of the present invention, a concurrent slitting andpreforming operation provides a plurality of longitudinally extendingcomponents comprising slit segments elongated by deformation out of theplane of the strip and unslit segments retained in the plane of thestrip. The unslit segments together define continuous bands extendinglaterally across a portion of the strip contained between longitudinallyextending edge portions of the strip. Since these bands contain all thebonds which connect adjacent components, these bonds are not undesirablydeformed as slit segments are moved out of the plane of the strip toprovide meshes extending substantially normal to the plane of the strip.The above-mentioned elongation of wire segments out of the plane of thestrip concurrent with slitting compensates for edge shortening thatwould otherwise occur in the subsequent lateral expansion of the strip.In a second slitting step, the slits are extended in a staggeredrelation through alternate bands to permit lateral expansion of the slitportion of the strip. Because of the holding of the bands containing allthe bonds during slit segment elongation before the completion ofslitting, desired preferential concurrent elongation of the slitsegments as they are formed is achieved, substantially avoiding ruptureof the strands during mesh expansion or failure of strands at nodebonds.

The mesh sheet can be produced rapidly from continuously moving strip toexact final dimensions independent of strip material dimensions andcomposition.

The method and apparatus of our invention which thus substantiallyovercome disadvantages inherent in conventional rotary and reciprocatingmethods, comprise essentially the steps of concurrently slitting andpreforming at least a portion of strip contained within imperforateborder portions to provide one or more longitudinally extendingstrand-like components, said components comprising elongated slitsegments deformed out of the plane of the strip and unslit segmentsretained in the plane of the strip, said elongated slit segments beingsevered from laterally adjacent segments and said border portions andsubstantially convexly shaped from the plane of the strip whereby slitsegments in laterally adjacent components extend from opposite sides ofthe plane of the strip, and said unslit segments retained in the planeof the strip together define continuous bands extending laterally atleast the width of said one or more strand-like components across thesaid portion of the strip; slitting the strip at alternate bands toextend the slit segments in a staggered relation; and laterallyexpanding the slit preformed portion of the strip to form meshes bydrawing opposite longitudinal edges of the strip apart whereby theelongated segments form a network of substantially flattened meshesjoined by nodes wherein unslit portions of the bands provide bondsbetween adjacent components.

BRIEF DESCRIPTION OF THE DRAWINGS

The method and apparatus of the present invention will now be describedin detail, reference being made to the following drawings wherein:

FIG. 1 is a plan of the apparatus;

FIG. 2 is a side elevation of the apparatus;

FIG. 3 is side elevation of a modification of the slitting andpreforming assembly wherein a cluster of three rolls is used;

FIG. 4 is a side elevation of another modification of the slitting andpreforming assembly wherein a cluster of three rolls is used;

FIG. 5 is a side elevation of a further modification of the slitting andpreforming assembly wherein strip is successively acted upon by rollpairs;

FIG. 6 is a plan of strip after passing through the slitting andpreforming assembly;

FIG. 7 is an enlarged side elevation of a slit and preformed portion ofstrip showing a modification in which elongated slit segments areasymmetrically shaped;

FIG. 8 is a section of slit and preformed strip viewed along line 8--8of FIG. 6;

FIG. 9 is an enlarged section of a strip component having asymmetrically curved slit segment and showing a portion of a relatedtool disc;

FIG. 10 is a perspective view of the strip as it leaves the slitting andpreforming assembly showing slit segments offset from laterally adjacentslit segments;

FIG. 11 is an end elevation on line 11--11 of FIG. 3 showing engagementof discs to complete slitting of preformed strip;

FIG. 12 is an enlarged end elevation on line 11--11 of FIG. 3;

FIG. 13 is a plan of portions of the strip showing transition fromcompletion of slitting to completion of lateral expansion with offsetslit segments corresponding to the embodiment illustrated in FIG. 10;

FIG. 14 is a side elevation of the strip as shown in FIG. 13 includingflattening rolls;

FIG. 15 is a perspective view of the strip as shown in part of FIG. 13;

FIG. 16 is an end elevation showing lateral expansion means;

FIG. 17 is an end elevation showing guiding chain detail; and

FIG. 18 is a plan sketch of completely slit and expanded sheet beforecutting to make battery grids.

Like reference characters refer to like parts throughout the descriptionof the drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIGS. 1 to 3, strip 10 passes over guide roll 12 and entersvertically into slitting and preforming assembly 14 comprising a clusterof three rolls 16, 18 and 20, each roll having a plurality of spaceddiscs 22, 24 and 26 respectively. The discs have tooled peripheraledges. Moving strip is engaged successively between first and secondrolls 16 and 18 and between second and third rolls 18 and 20. Rolls 16and 18 act on rapidly advancing strip to provide upturned edges 28, FIG.6, in lateral edge portions 30 for engagement with expansion means, andto hold bands 32 extending between a central portion 34 of the strip andlateral portions 30 while substantially convexly shaped tool surfaces 36of discs 22 engage like tool surfaces 38 of discs 24 to slit portions 40of strip 10 between bands 32 and elongate slit segments 42 out of theplane of the strip. Tool surfaces 36 and 38 alternate with substantiallyflat portions 44 and 46 on their respective rolls and are equally spacedcircumferentially to provide interacting peripheral surfaces as therolls rotate. During rotation of the rolls, convexly shaped toolportions 36 of a disc 22 of first roll 16 are engaged by convexly shapedtool portions 38 of adjacent discs 24 of second roll 18 to providelongitudinal slits as the curved surfaces 36 penetrate through the planeof the strip to stretch slit segments 42 between slits 48 into spaces 50which are between adjacent discs 24 of second roll 18. Then,substantially flat portions 44 and 46 of the discs of both rolls becomecircumferentially aligned and spaced from each other to hold unslitsegments which together form laterally extending bands 32. In the samemanner, convexly shaped tool portions 38 of a disc 24 of second roll 18penetrate through the plane of the strip in the opposite direction tostretch slit segments 54 into spaces 56 between adjacent first rolldiscs 22, on the opposite side of the plane of strip 10. In line witheach disc 22 there is formed in the strip a component 58, FIG. 7,comprising slit segments 42 deformed out of the plane of the strip inone direction spaced by unslit segments 52 retained in the plane of thestrip. These components alternate with like components in line with eachdisc 24 and having slit segments 54 deformed out of the plane of thestrip in the opposite direction. The unslit segments of all thecomponents together define continuous bands 32 extending across the flatportions 44 and 46 of discs 22 and 24 respectively.

As the strip leaves the area of engagement of rolls 16 and 18, a set ofstripper bars 60 assures separation of preformed strip from first roll16. Preformed strip 62, FIG. 10, has upturned edges 28 in lateral edgeportions 30, central unslit portion 34 and intermediate slit andpreformed portions 64 and 66 each comprising longitudinally extendingstrip components 58. Each strip component 58, FIG. 7, has elongated slitsegments 42 or 54 alternating with unslit segments 52. Slit segments 42of alternate components 58 extend from one side of the plane of thestrip while slit segments 54 of laterally adjacent components 58 extendfrom the other side of the plane of the strip. In the modification asshown in FIG. 7, slit segments 42 and 54 are asymmetrically shaped andare formed by correspondingly shaped tool surfaces 36 and 38 in FIG. 3.This structure is shown in lateral cross section in FIG. 8. In a simplermodification of the invention, FIG. 9, strip components 58 havesymmetrically shaped elongated slit segments 68, formed bycorrespondingly curved tool surfaces 70 of discs 22 and 24. This form isshown in perspective in FIG. 10.

FIG. 10 also shows a modification of the invention which may be usedwhen two or more portions across the width of the strip are slit andpreformed. In the providing of laterally extending bands 32 and slitsegments 42 and 54 in the slitting and preforming operation, the cuttingforces alternate between minimum when flat portions 44 and 46 becomecircumferentially aligned to hold bands 32 and maximum when toolsurfaces 36 and 28 penetrate the strip. This cycle change betweencutting and not cutting of the strip causes vibration in the roll drivemeans. The vibration may increase as strip is moved more rapidly throughthe assembly. In the slitting of portions 64 and 66 of the strip it isadvantageous for the tool surfaces and which engage portions 64 to beout of phase with the tool surfaces and which engage portion 66. Then,as a set of laterally aligned tool surfaces initiates penetration intomesh area 64 another set of laterally aligned tool surfaces iscompleting the formation of slit segments in mesh area 66 andapproaching engagement of bands 32. Cutting forces are more uniformlydistributed during rotation and smoother operation results. If more thantwo portions of strip are slit and preformed, circumferentialdistribution of the points of entry will provide still smootheroperation.

On being released from roll 16, preformed strip 62 follows second roll18 for a convenient distance, e.g. a quarter turn as shown in FIG. 3, toan area of engagement of second roll 18 and third roll 20 which hasspaced discs 26 with disc components 74 consisting of effective cuttingedges 72 and recesses 75, FIGS. 3, 11 and 12, which are spacedcircumferentially to align, on alternate sides, on rotation of therolls, with like disc components 76 consisting of recesses 77 andcutting edges 79 in discs 24 of second roll 18 which extendcircumferentially from alternative flat portions 46 to permit passage,without slitting, of alternate bands in each line of slits formedbetween adjacent components 58 by engagement of the first and secondrolls. Like recesses 75 or 77 occur in alternating positions in theopposite faces of the discs of both the second and third rolls. Cuttingedges 72 of the disc peripheries penetrated through the strip to extendthe slits 48 through alternate bands 32 in a staggered relation, thuscompleting two-step slitting, which permits lateral divergence of stripedges to form diamond-shaped meshes. FIG. 11 also shows relative smalldiameter spacer discs 78 which are placed between adjacent discs 22, 24and 26 of the three rolls.

As the strip leaves the area of engagement of the second and third rolls18 and 20, a set of stripper bars 80 guides the preformed and completelyslit strip away from the third roll, and a set of stripper plates 82supported on an adjacent shaft 84 and restrained against rotationproject into the spaces between adjacent discs of the second roll toguide elongated slit segments 42 away from the second roll. Since thestrip never leaves the second roll while moving through the assembly,good registry of the strip with all cutting and preforming tool faces ismaintained. Thus slits 48 in FIG. 6 are alternately extended to providethe staggered pattern of slits 86 in FIG. 13 in a manner which avoidscutting into and weakening of intermediate bonds 88 between adjacentcomponents. Completely slit and preformed strip, partially expanded, isshown in perspective in FIG. 15.

In the modification of the foregoing description, strip is movedvertically for engagement between the first and second rolls, followsthe second roll through a quarter turn, and moves horizontally betweenthe second and third rolls. Guide roll 12 directly above first roll 16may be used to direct horizontally moving strip into the slitting andpreforming assembly. In another modification, FIG. 4, second roll 18 isplaced above first roll 16. Strip 10 moving horizontally between firstand second rolls 16 and 18 follows the second roll through a quarterturn for engagement between second roll 18 and third roll 20 and thenfollows the third roll through a quarter turn to exit horizontally. Aset of stripper bars 89 assures separation of preformed strip from firstroll 16, but, since passage of strip interferes with two ended mountingof stripper bars, sets of stripper plates 90 and 92 are used to guidepreformed and completely slit strip away from second roll 18 and thirdroll 20 respectively. Symmetrically curved tool surfaces 70 are shown inFIG. 4.

According to the modification shown in FIG. 3, forming of upturned edgescan be effected between the first and second rolls. These upturned edgesare bent only once, as the strip changes direction to follow the secondroll. Upturned edges can be formed between the last pair of opposedrolls to avoid bending of the edges. In the FIG. 4 modification, theupturned edges are bent twice, while engaging the second and thirdrolls. Alternatively, separate tooling, such as opposed forming rolls,may be provided in advance of the roll clusters of both modifications toprovide the upturned edges.

Slitting and preforming may also be carried out using an assembly, 94,FIG. 5, in which pairs of rolls are arranged in a line so that movingstrip 10 passes through the assembly without being bent. The rolls ofpair 96 provide slitting and preforming of slit segments 98 as bands 100comprising unslit segments are retained in the plane of the strip. Therolls of pair 102 act to complete the slitting which permits lateralopening of mesh diamonds. Conventional stripper bars 104 are used tokeep the strip from following the rolls of these pairs. Forming ofupturned edges on the lateral edges 106 of the strip may be done using athird pair of rolls 108 which may be placed in advance of the other twopairs. This in-line arrangement has an advantage in that stripping ofengaged slit segments is facilitated. Proper registry and surface speedcontrol of the moving strip with the tool faces depend onsynchronization and adjustment of external drive means and are moredifficult to obtain than the registry and speed control obtained by thecluster of three coacting rolls. Engagement of the tool surfaces withthe moving strip is essentially the same in all the modifications.

In the foregoing descriptions, two portions of the width of strip areprepared for lateral expansion by a slitting and preforming operation inwhich slitting is carried out in two steps. Meshes are formed in twoportions of sheet each bounded by a lateral edge portion and a centralportion of sheet which is not slit. Without changing the method of theinvention, a single strip portion or a plurality of strip portions, eachdisposed between portions of strip which are not slit, may be preparedfor lateral expansion. In the expansion of a plurality of stripportions, unslit portions which are not lateral edges may be guided in aknown manner such as by divergence of pairs of silent chains providedwith spaced pins which penetrate into or through these unslit portions.The number of components in each slit portion is not critical. Themethod of slitting and preforming in one step followed by completion ofslitting in a second step may be applied to a very narrow slit areacomprising only one component spaced between two imperforate borderportions.

Opening of mesh diamonds 110, FIG. 13, is effected by causing thelateral edges 30 of preformed and completely slit strip to diverge, e.g.by engagement by guiding means such as pairs 112 of silent chains, FIG.16, moving in diverging paths 114, FIG. 1. If the slitting andpreforming operation provides two mesh areas between a central unslitportion 34 and respective lateral edges 30, it is convenient to restrainthe central unslit portion 34 against movement to either side as lateraledges 30 diverge. This may be done by pressure engagement between silentchains 116. With this restraint, slit and preformed portions 64 and 66of the strip do not have to be alike. Various gripping means may beapplied to the lateral edges. Preferably, narrow upturned edges 28formed along lateral portions 30 of the strip are engaged by recesses118, FIG. 17, in multiple link silent chains. Conveniently, theserecesses may be made by cutting away portions of rows of links which areadjacent the innermost row of links 120 of each of two upper chains 122.Enough links, usually two or three, to accommodate the thickness of thestrip are cut to a depth which does not expose laterally extendingconnecting pins. As upturned edge 28 at one side of the strip entersinto recess 118 of an endless upper chain 122, a lower chain 124 isbrought into pressure engagement with the underside of the stripdirectly below the upper chain, both chains following the same pathduring divergence. Preferably one of the chains, upper chain 122 in FIG.17, rides on a plate 126 which is resiliently biased, e.g. by aplurality of coiled springs 128, towards the chain. Alternatively, thelateral edges of the strip may be troughed by engagement betweencomplementary pairs of rolls, with the troughs being retained bydiverging guiding means, or pins attached to the inner edges of theguiding means may penetrate into or through the lateral portions of thestrip.

During divergence of the lateral portions of strip to open meshdiamonds, it is advantageous, particularly with materials such as leadand lead alloys wherein the tensile strength of the bonds is less thanthe tensile force required to straighten the convexly shaped portions ofthe components, to provide pressure assistance to move elongated wiresegments towards the plane of the strip in a plurality of steps. Forexample, in the preforming of 1 mm thick strip, the nominal thickness,i.e. the spacing between peaks of elongated wire segments on oppositesides of the strip, may be increased to 6 mm. Passing of laterallyexpanding strip successively between one or more pairs of rolls e.g.rolls 130, 132 and 134 in FIG. 14 having, for example, 5, 3, and 2 mmspacings, will bring the wire segments substantially into the plane ofcompletely slit and expanded sheet 136 in a controlled manner. Expansionis effected with less laterally directed force on bonds between meshstrands, thus providing effective control against breakage of bonds.

In prior art methods of preparing strip for expansion, it is usual toform the pattern of staggered slits which is essential to permit lateralexpansion, either completely or in interrelated steps, in advance ofelongations required to compensate for shortening of mesh portions ofthe strip. During elongation, nodes, each having four attached slitsegments, are pushed out of the plane of the strip. On lateralexpension, rotational forces act on these nodes. Bending occurs at thenodes during both expansion and subsequent flattening to bring the nodesinto the plane of expanded sheet. In the method of the presentapplication, preforming does not move nodes out of the plane of thestrip and forces which may damage nodes being returned to the plane ofthe strip are avoided. Firm holding of bands which extend across thestrip and exclusion of nodes from elongated portions provide bettercontrol over these portions of strip during slitting and preforming.

In tests in which completely slit strip was preformed by rolls havingdiscs with convexly shaped tool surfaces having the length of a node andtwo adjacent slit segments plus calculated required elongation, as inthe prior art arrangements, we observed a tendency for the spacingbetween the leading and trailing ends of the slits to decrease, thusindicating a shortening of the slit portion of strip relative to theimperforate borders. Apparently the portions of strip componentsengaging the tool surfaces were partly elongated and partly corrugatedor shaped without stretching. In the method of the present invention, inwhich slit segments only were engaged by convexly shaped tool surfaces,predetermined elongation was substantially completely effected. Themethod of the patent application thus provides high speed rotaryslitting and preforming plus lateral expansion as strip movescontinuously through the assembly.

As shown in FIG. 18, battery grids may be obtained from expanded sheet136 which has been prepared by described modifications of the invention.Laterally oriented grids 138 and their tabs 140 may be separated fromsheet 136 by removal of scrap material 142 between tabs 140, slitting ofthe strip to separate the ends of the tabs from adjacent grids andcutting of the strip into appropriate grid lengths. Upturned guidingedges 28 may be flattened or may be removed by trimming.

In roll preforming of wires from strip having conventionally staggeredrows of slits, no advantage has been shown for the use of discs whichhave wire elongating portions that are other than symmetrically shaped.In the production of metal lath from steel strip, for example, wireshave sufficient tensile strength to permit stretching without localizedweakening that may affect their usefulness. In the preforming of lead orlead alloy wire segments on symmetrically shaped tooling surfaces, wehave observed that areas of weakness occur near the trailing ends ofelongated wire segments as the strip is advanced through the slittingand preforming assembly. As disclosed in detail in copending CanadianPatent Application No. 315190 filed Oct. 31, 1978, we have determinedexperimentally that the slit segments are more uniformly stressed if thesubstantially convexly curved tooling surfaces are asymmetrically shapedwith their apices in advance of the centre lines between the entry andtrailing ends of the tooling surfaces. This asymmetrical shaping isshown most clearly in FIG. 7.

In the slitting, preforming and expanding of two or more portions ofstrip which are spaced by unslit portions, it is not necessary toprovide identical mesh patterns in separate lines such as portions 64and 66 of FIG. 10. For example, positive grid meshes may be formed inone line and negative grid meshes in another. Engagement of unslit stripportions between the lines of mesh by spring biased silent chainsrestrains the strip against lateral movement that might otherwise becaused by unequal forces required to open differently sized diamonds.

The process of the present invention provides a number of importantadvantages. Concurrent slitting of strip material and deformation ofstrand segments as they are formed substantially avoids breakage ofstrands due to excess stretching or concentration of stresses at nodesoften encountered in sequential operations such as rotary slittingfollowed by a separate stretching step. Reciprocal forming may permitconcurrent slitting and stretching together with mesh expansion but thedimensions of the finished product are sensitive to and dependent onstrip material thickness and composition. Variations in mesh finaldimensions, not permissible in the manufacture of close tolerancebattery grids, thus result from variations in strip thickness when usingreciprocating methods. Overall grid dimensions having close tolerancescan be produced at higher rates of production using the process of thepresent invention.

The present process permits forming of profile strip having a variablethickness, such as tapered strip intended to have increased amperagecapacity in proximity to the support tabs.

What we claim as new and desire to protect by Letters Patent of the United States is:
 1. An apparatus for expanding metal strip comprising, in combination, a first pair of opposed rolls each having means for concurrently slitting and preforming at least a portion of said strip to provide a plurality of longitudinally extending strand-like components, said strand-like components comprising slit segments deformed out of the plane of the strip and unslit segments retained in the plane of the strip, said slit and deformed segments severed from laterally adjacent segments and substantially convexly curved from the plane of the strip whereby slit segments in laterally adjacent components extend from opposite sides of the plane of the strip and said unslit segments retained in the plane of the strip together define continuous bands extending laterally across the said portion of the strip, a second pair of opposed rolls each having means for slitting the strip at alternate bands to extend the slits in a staggered relation, and means for expanding the slit and preformed portion of the strip to form meshes by drawing opposite longitudinal edges of the strip apart whereby the curved segments are substantially straightened to form webs of the mesh joined by nodes formed by unslit portions of the bands.
 2. An apparatus as claimed in claim 1 in which each of said first pair of opposed rolls comprises a plurality of equispaced discs having circumferential, equally spaced convexly shaped tool surfaces alternating with substantially flat surfaces whereby peripheral surfaces of opposing rolls interact on strip passing therebetween to preform slit segments by said convexly shaped tool surfaces and define continuous lateral unslit bands by said substantially flat surfaces.
 3. An apparatus as claimed in claim 2 in which the discs of the second pair of opposed rolls additionally include cutting edges and radial recesses alternating on opposite sides of peripheral flat surfaces whereby lateral bands are slit to extend preformed slit segments in a staggered relation.
 4. An apparatus as claimed in claim 3 in which said first and second pairs of opposed rolls have a common roll whereby said rolls together define a cluster of three parallel rolls.
 5. An apparatus as claimed in claim 3 in which said first and second pairs of opposed rolls have a common roll and in which the rolls comprising said first pair of rolls are disposed in a substantially horizontal interacting relationship with each other and said second pair of rolls are arranged in a substantially vertical interacting relationship with each other whereby metal strip can be fed vertically to said first pair of rolls and discharged horizontally from said second pair of rolls.
 6. An apparatus as claimed in claim 3 in which said first and second pairs of opposed rolls have a common roll and in which the rolls comprising said first pair of rolls are disposed in a substantially vertical interacting relationship with each other and said second pair of rolls are arranged in a substantially horizontal interacting relationship with each other whereby metal strip can be fed horizontally to said first pair of rolls and discharged horizontally from said second pair of rolls.
 7. An apparatus as claimed in claim 3 in which said first and second pairs of rolls are arranged in line whereby strip passes linearly through said rolls.
 8. An apparatus as claimed in claim 7 in which forming rolls are positioned in advance of said first pair or folls whereby an upturned edge can be formed on each lateral edge of strip passing therethrough.
 9. An apparatus as claimed in claim 5, 6 or 7 in which said means for expanding the slit and preformed portion of the strip comprises gripping and guiding means for engaging opposite longitudinal edges of the strip and advancing said edges in diverging paths whereby said strip is progressively laterally expanded.
 10. An apparatus as claimed in claim 9 in which said gripping and guiding means comprises two spaced apart pairs of opposed endless chains adapted to grip the opposite longitudinal edges of the strip therebetween.
 11. An apparatus as claimed in claim 10 in which one chain in each pair of opposed endless chains has a longitudinal recess formed therein for engaging an upturned edge formed along each longitudinal edge of the strip and biasing means for resiliently urging the chains comprising each pair of opposed chains towards each other.
 12. An apparatus as claimed in claim 11 in which an additional pair of opposed endless chains is disposed intermediate said spaced apart pairs of endless chains to grip a central unslit portion of the strip for restraining the central portion of the strip against lateral movement.
 13. An apparatus as claimed in claim 2 in which longitudinally extending elongated stripper bars or plates are stationed between the discs comprising each roll for stripping slit and preformed strip from said roll.
 14. An apparatus as claimed in claim 5, 6 or 7 in which at least one pair of opposed rolls is disposed after said second pair of rolls for flattening wire segments substantially into the plane of strip passing therebetween.
 15. An apparatus as claimed in claim 5, 6 or 7 in which the convexly shaped tool surfaces are symmetrically shaped.
 16. An apparatus as claimed in claim 5, 6 or 7 in which the convexly shaped tool surfaces are asymmetrically shaped. 